Coiling arrangements used for coiling a strip are generally known, such as for example from EP 0 790 084 B1 for a steel rolling mill.
Coiling arrangements are used both in hot rolling and in cold rolling, that is to say also below the recrystallization temperature. For example, a steel strip is first coiled in a hot rolling mill, sent in this coiled form to a cold rolling mill, and uncoiled again there for cold rolling. In the cold rolling mill, there may therefore be both an uncoiling coiler and, at the end of the mill, a tensioning coiler for coiling. If operating in reversing mode, i.e. if the strip moves through the cold rolling mill in both directions, there may also be a tensioning coiler on both sides. In connection with the invention, the uncoiling and coiling are both referred to below by the subsumptive term coiling.
It is also known to operate a coiler in rolling mills under speed override and with a fixed torque limit. In this case, a control device prescribes to the coiler a setpoint coiler speed and a coiler limiting moment, acting in the running direction of the strip. Similarly, the control device prescribes to a driving roller a setpoint roller speed and both a roller limiting moment acting in the running direction of the strip and a roller limiting moment acting counter to the running direction of the strip, and so the control device also operates the driving roller in a speed-controlled and moment-limited manner.
In the case of known coiling arrangements, there is the problem that variations occur in the tension of the strip. The increased tension may in this case be so great that it exceeds the yield point of the strip, that is to say leads to plastic deformations, for example constrictions, of the strip. The thickness, and in particular also the width, of the strip to be coiled may vary as a result. Loss of constant thickness and width of the strip to be wound represents a loss of quality. In AT 408 526 B there is described, for example, a method for reducing fluctuations in the tensile force during coiling, such fluctuations in the tensile force being described as being caused by instances of out-of-roundness in the region of the coiler. For correction, the respectively current tensile force and the respectively current angle of twist of the coiler are determined.